Denitrification in sediment determined from nitrogen isotope pairing

Abstract

A new method for accurate and easy measurement of denitrification in sediments is presented. The water overlying intact sediment cores was enriched with "NO.; which mixed with the 14NO; of the natural sources of NO;. The formation by denitrification of single-labeled (I4NI5N) and double-labeled ("N"N) dinitrogen pairs was measured by mass spectrometry after a few hours incubation. Total denitrification including the formation of unlabeled ft4NI4N) dinitrogen could be calculated assuming random isotope pairing by denitrification of the uniformly mixed NO; species. In contrast to previous approaches, by this method it is possible to measure denitrification of both NO, diffusing from the overlying water and NO; from nitrification within the sediment.